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Objectives: Existing data on bonobo and chimpanzee dental eruption timing are derived predominantly from captive individuals or deceased wild individuals. However, recent advances in noninvasive photographic monitoring of living, wild apes have enabled researchers to characterize dental eruption in relatively healthy individuals under naturalistic conditions. At present, such data are available for only one population of wild chimpanzees. We report data for an additional population of wild chimpanzees and the first dental eruption data for wild bonobos. Materials and Methods: We collected photographs and video footage of teeth from the open mouths of wild bonobos and East African chimpanzees of known age from LuiKotale, Democratic Republic of the Congo, and Gombe National Park, Tanzania, respectively. We scored the presence and absence of deciduous teeth from photographs and video footage to characterize deciduous dental eruption timing in these two populations. Results: Deciduous dental eruption ages in our sample fall within the range of variation previously documented for captive chimpanzees, but eruption ages are later in wild than in captive contexts. We found substantial variation in deciduous canine eruption timing, particularly among bonobos. One bonobo had a deciduous canine present by 227 days old while another did not have a deciduous canine present at 477 days old. Discussion Our data indicate that deciduous teeth erupt later in wild individuals than in captive individuals. We also found that deciduous dental eruption timing varies considerably between individuals within our study populations, a pattern that is consistent with previous studies. Future studies should consider sources of variation in deciduous canine eruption timing and relationships with other aspects of life history as additional data become available. [ABSTRACT FROM AUTHOR]

Objectives: A key feature of human life history evolution is that modern humans wean their infants 2–4 years earlier on average than African apes. However, our understanding of weaning variation in apes remains limited. Here we provide the first such report in chimpanzees by examining weaned age variation using long‐term data from Gombe National Park, Tanzania. Material and Methods: We analyzed 41 years of observational behavioral data from 65 offspring of 29 mothers to examine the relationships between weaned age (defined as cessation of suckling) in wild chimpanzees and maternal age, dominance rank and parity, and offspring sex. We used Cox proportional hazards regression with mixed effects to model time to weaning and to examine potential sources of variation in offspring weaned age. Results: We found that male offspring were less likely than female offspring to wean by a given age and that weaned age of males varied more than weaned age of females. In addition, maternal dominance rank interacted with offspring age, such that low‐ranking mothers were less likely to wean offspring early, but this effect decreased with offspring age. Discussion: We found that male offspring and offspring of low‐ranking females were less likely to wean early, but did not find evidence for variable weaning according to maternal age or parity. As more data accumulate, we will be better able to disentangle the effects of maternal dominance rank, age and parity. Such studies will not only provide a richer understanding of living ape life history characteristics, but will also provide an important framework for understanding the evolution of early weaning in humans. [ABSTRACT FROM AUTHOR]

Immunoglobulin A (IgA) is the primary antibody responsible for mucosal defense in mammals and has been used as a marker for chronic stress and immune status. Therefore, this antibody may provide a more reliable indicator of an individual's immunocompetence than is currently available through other methods. Immunoglobulin A has never before been quantified in a wild population of non‐human primates using non‐invasive sample collection techniques. In this study, we present methodology for non‐invasive IgA extraction in the field and provide quantification of mean fecal IgA concentrations in wild chimpanzees (Pan troglodytes schweinfurthii). During the study period (November 2009–October 2010), we collected fecal samples (N = 1463) from 59 individuals at Gombe National Park, Tanzania. We modified a field extraction technique for steroidal hormones to extract IgA from the fecal samples and then quantified mean IgA concentrations (ng/g) using a commercial human IgA enzyme immunoassay. Mean IgA concentration varied among individuals but not by sex or reproductive status. Mature animals tended toward higher mean IgA concentration than immature. Mean IgA concentration differed by quartile season, following a similar pattern previously observed for respiratory illness rates in this population, with the late dry season having significantly higher averages than the late wet. A circadian rhythm was also evident with mean IgA concentrations higher in samples collected in the latter half of the day. These demographic and temporal patterns of IgA concentration provide baseline values necessary to interpret future results, which may be combined with other health values to better understand the role of health and long‐term stress in wild great ape populations. Am. J. Primatol. 80:e22558, 2018. © 2016 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Disease and other health hazards pose serious threats to the persistence of wild ape populations. The total chimpanzee population at Gombe National Park, Tanzania, has declined from an estimated 120 to 150 individuals in the 1960's to around 100 individuals by the end of 2013, with death associated with observable signs of disease as the leading cause of mortality. In 2004, we began a non‐invasive health‐monitoring program in the two habituated communities in the park (Kasekela and Mitumba) with the aim of understanding the prevalence of health issues in the population, and identifying the presence and impacts of various pathogens. Here we present prospectively collected data on clinical signs (observable changes in health) in the chimpanzees of the Kasekela (n = 81) and Mitumba (n = 32) communities over an 8‐year period (2005–2012). First, we take a population approach and analyze prevalence of clinical signs in five different categories: gastrointestinal system (diarrhea), body condition (estimated weight loss), respiratory system (coughing, sneezing etc.), wounds/lameness, and dermatologic issues by year, month, and community membership. Mean monthly prevalence of each clinical sign per community varied, but typically affected <10% of observed individuals. Secondly, we analyze the presence of clinical signs in these categories as they relate to individual demographic and social factors (age, sex, and dominance rank) and simian immunodeficiency virus (SIVcpz) infection status. Adults have higher odds of being observed with diarrhea, loss of body condition, and wounds or lameness when compared to immatures, while males have a higher probability of being observed with wounds or lameness than females. In contrast, signs of respiratory illness appear not to be related to chimpanzee‐specific factors and skin abnormalities are very rare. For a subset of known‐rank individuals, dominance rank predicts the probability of wounding/lameness in adult males, but does not predict any adverse clinical signs in adult females. Instead, adult females with SIVcpz infection are more likely to be observed with diarrhea, a finding that warrants further investigation. Comparable data are needed from other sites to determine whether the prevalence of clinical signs we observe are relatively high or low, as well as to more fully understand the factors influencing health of wild apes at both the population and individual level. Am. J. Primatol. 80:e22562, 2018. © 2016 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Social play is common among many group-living animals, but the benefits are not well understood. Proposed benefits include increased muscle coordination as the result of increased locomotor versatility and development, and strengthened social bonds through interactions with like-aged individuals. In this study, we used 33 years of long-term behavioral data on infant chimpanzees in Gombe National Park, Tanzania, to examine these potential benefits of social play, specifically how the percentage of time engaged in social play relates to motor and social developmental milestones. We predicted that infants who engaged in more social play would achieve motor and social milestones at younger ages. We found that individuals that spent more time engaging in social play achieved the motor milestones of riding dorsally and traveling independently at earlier ages. Additionally, we found that the amount of play was correlated with earlier ages for reaching the social milestones of spatial independence from mother, first grooming of non-maternal kin, and first observed mating attempt. This is the first study in great apes to demonstrate a relationship between play behavior and developmental milestones, supporting the hypotheses that play provides motor, and social benefits. [ABSTRACT FROM AUTHOR]

Chimpanzees exhibit cultural variation, yet examples of successful cultural transmission between wild communities are lacking. Here we provide the first account of tool-assisted predation ("ant fishing") on Camponotus ants by the Kasekela and Mitumba communities of Gombe National Park. We then consider three hypotheses for the appearance and spread of this behavior in Kasekela: (1) changes in prey availability or other environmental factors, (2) innovation, sod (3) introduction. Ant fishing was recognized as habitual in the Mitumba community by 1992, soon after their habituation began. Apart from one session in 1978, Camponotus predation (typically with tools) was documented in the Kasekela community beginning only in 1994, despite decades of prior observation. By February 2010, ant fishing was customary in Kasekela and with one exception was practiced exclusively by chimpanzees born after 1981 and immigrant females. We hypothesize that changes insect prey availability over time and/or the characteristics of one popular ant-fishing site may have influenced the establishment of ant fishing. Though innovation cannot be completely ruled out, the circumstantial evidence suggests that a Mitumba immigrant introduced ant fishing to Kasekela. We submit that this report represents the first documented case of successful transmission of a novel cultural behavior between wild chimpanzee communities. [ABSTRACT FROM AUTHOR]

Researchers have reported a total of 31 infanticides in 4 different chimpanzee (Pan troglodytes) populations. Though infanticide is infrequent, low reproductive rates of females likely make it a strong selective pressure in the species. We report a new incident of intragroup infanticide in Gombe National Park, Tanzania, in which a community male attacked a 3.5-yr-old male. We then consider the infanticide in terms of adaptive and nonadaptive explanations for infanticide including the social pathology, by-product of male aggression, nutritive benefits, resource competition, and sexual selection hypotheses. The incident reported here is not well explained by any of them. While the infanticide is puzzling in terms of ultimate explanations for infanticide, it provides a good context in which to consider proximate mechanisms for offspring recognition. The incident provides some evidence that males may use their mating history with the mother to assess paternity likelihood. [ABSTRACT FROM AUTHOR]